Yes, I only use the "A" setting when I'm feeling very lazy. You can use this camera in full manual mode, so if you have a handheld meter, you can shoot away. Setting the aperture dial to "A" is what sets the camera to "shutter priority" mode, and selects the aperture according to the shutter speed you've chosen.
The lightmeter dial in the viewfinder/rangefinder shows which aperture will be used according to the shutter speed you've selected. Again, the lightmeter is only on when you set the "A" aperture dial. It will always be on if you leave the dial set to "A", so always remember to set it to an actual aperture number when you're going to put your QL G-III away.
Also, the shutter won't fire if, when you're using the "A" mode, it's either overexposed or underexposed, according to its lightmeter.